I’ll agree 100% that the metronome is the most efficient way to get the fretting synched up with the picking, but I disagree vehemently with any claim that the metronome is necessary for the “athletic” component of speed development.
Speed training in athletic domains is not a regimented incrementaly measured endeavor like weight training is.
World class sprinters like Usain Bolt don’t train their cadence with a metronome, gradually working up from low BPM to fast. Sure, sometimes they’ll work at less than their maximum speed in order to perform technique optimization, but that’s not about locking into a specific sub-max tempo, it’s about going slow enough to be able to make prescribed corrections to technique, regardless of the exact tempo.
And sometimes sprinters do practice where they are trying to maintain a consistent tempo, but that’s again about finding a technique sweet spot below maximum speed, not about matching tempo to an external rhythm.
And if we look to nature, cheetahs, horses and foxes don’t learn to run fast by using a metronome.
Is metronome training in music important? Absolutely. But it’s importance isn’t in connections with the raw athletic component of speed development. When it comes to doing something musical with whatever speed you do have? Yeah, absolutely there needs to be metronome work.